AAAAI: Mice Prone to Asthma After Fetal BPA Exposure

Action Points

Explain to interested patients that BPA is a chemical found in many plastics and that the FDA has recommended that pregnant women and nursing mothers avoid exposure themselves and also avoid using BPA-containing plastic baby bottles to feed their infants.

Explain that this study was conducted in mice and involved an artificially induced form of asthma that differs in some ways from the human disease. The results should not be interpreted to apply to humans until they are confirmed in clinical studies.

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.

NEW ORLEANS -- As with several other possible triggers for asthma, fetal exposure to the plastics chemical bisphenol A (BPA) could be more important than postnatal exposures, said researchers conducting a study in mice.

Mouse pups were more likely to develop an asthma-like syndrome when they were exposed to BPA in utero compared with no exposure, and also compared with exposure only through their milk after birth, reported Randall Goldblum, MD, of the University of Texas Medical Branch in Galveston.

"It's the prenatal dose that they're getting that sets the point for developing asthma," said Goldblum at a poster presentation here at the American Academy of Allergy, Asthma & Immunology annual meeting. "We think that's the critical period."

The study could have implications for current recommendations on BPA exposure. The FDA has recommended that nursing mothers and pregnant women avoid exposure to BPA as much as possible, and also that parents avoid using baby bottles made of plastics that contain BPA.

In the UT-Galveston study, pregnant mice were fed water laced with various levels of BPA, from zero up to 10 μg/mL. Serum levels in the dams and their pups were measured at 22 days after birth.

The primary outcome was the development of experimental asthma following inhalation of ovalbumin shortly after birth.

Goldblum and colleagues found that airway eosinophils, allergen-specific IgE production, and airway hyper-responsiveness were all increased in the pups whose mothers were fed the highest dose of10-μg/mL dose of BPA.

For example, in methacholine challenge testing, a standard measure of airway responsiveness, a 30-mg/mL dose led to a 450% change in airway flow, compared with about 200% in pups not exposed to BPA (P<0.05).

The difference was even greater when airway responsiveness was measured with whole body barometric plethysmography (1,000% versus 400%, P<0.05, at 30 mg/mL methacholine).

The testing revealed that hyper-responsiveness was limited to those pups whose exposure was prenatal. Pups born to mice not fed BPA during pregnancy, but nursed by mothers drinking the BPA-laced water, were only half as responsive to the 30-mg/mL dose of methacholine (P<0.05) as pups with BPA-fed mothers in pregnancy but which were switched after birth to nursing females not given BPA.

Airway responsiveness in the pups whose only exposure was postnatal was the same as in mice with no exposure at all.

Goldblum also emphasized a finding that serum levels of BPA in the 22-day-old pups was significantly higher than in their mothers.

Mothers fed BPA at 0.1 μg/mL had mean serum levels of about 2 ng/mL, but serum BPA ranged from about 10 to 30 ng/mL in their pups.

"The most likely reason is that the pups do not express the gene for the major [toxin-metabolizing] enzymes," Goldblum said.

He noted that the FDA has advised women to avoid BPA as much as possible during pregnancy and while breastfeeding. But if the findings from this mouse study are confirmed in humans, that advice might need re-evaluation, he suggested.

"Nursing may not be as important as what you have when you get pregnant," Goldblum said.

W. Elliott Horner, PhD, a specialist in the health effects of environmental contaminants at Air Quality Sciences in Atlanta, said these and other findings reported here at the AAAAI meeting were building a strong case regarding fetal versus postnatal exposures.

"I think the in utero exposures are going to be very important for a variety of things," said Horner, who was not involved with the study. "This [BPA study] is particularly important for looking at the milieu of the chemicals to which we are exposed -- in this case, through dietary exposure, but also what's important in the indoor environment."

The study was funded by the National Institute of Environmental Health Sciences.

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